1. Field of the Invention
The invention relates generally to oil seals used for sealing a rotatable shaft extending through a housing.
2. Related Art
Dynamic oil seals often employ a sealing disc or wafer made of polytetrafluoroethylene (PTFE) for its superior sealing properties. The PTFE water is typically clamped between inner and outer case members. The multi-piece case is then pressed into engagement with a metal carrier for mounting on a housing or the like about a rotating shaft to be sealed. The multi-piece construction of the carrier/case lends itself to multiple forming operations and assembly steps to prepare such a seal. In one such operation, the axially outer edge of the outer carrier member is curled in a forming operation about the end of the inner case member to secure the PTFE disc therebetween in an axially compressed condition. The curling operation requires special forming equipment and adds cost and complexity to the process of forming seals.
It is an object of the present invention to simplify the manufacture and construction of dynamic oil seals.
A dynamic seal assembly constructed according to the invention comprises a one-piece annular carrier member having a radially outwardly extending mounting flange presenting an axially outwardly facing surface and an opposite axially inwardly facing surface. The carrier includes a seal flange spaced radially from and extending radially inwardly of the mounting flange and presenting axially outwardly and inwardly facing surfaces. An intermediate portion of the carrier extends between and interconnects the flanges and presents a first annular shoulder extending axially inwardly of the mounting flange and a second annular shoulder extending axially inwardly from the seal flange. The assembly includes an annular PTFE seal member having a radially outer edge portion and a radially inner edge portion. The seal member is disposed on the second shoulder of the carrier member with the radially outer edge portion of the seal adjacent the axially inwardly facing surface of the seal flange, and with the radially inner portion of the seal extending radially inwardly of the seal flange to present an annular sealing lip for sealing about a rotating shaft. The assembly further includes an inner annular case member disposed about the second shoulder of the carrier and staked to the second shoulder in position to compress and securely clamp the radially outer edge portion of the PTFE seal member axially between the case member and seal flange.
The invention further provides a method of fabricating a dynamic seal assembly which comprises preparing a one-piece carrier member having the aforementioned mounting and seal flanges as well as the intermediate portion and the annular PTFE sealing disc having the radially outer and radially inner portions. The radially outer portion of the sealing disc is disposed about the second shoulder of the carrier after which a case member is disposed about the second shoulder. The case member is forced axially toward the seal flange of the carrier to compress the radially outer portion of the sealing disc axially between the case member and the carrier. While the sealing disc is axially compressed, the case member is staked to the carrier to secure the case member on the carrier and to retain the sealing disc in the compressed condition.
One advantage of the invention is that a one-piece carrier is provided along with a one-piece inner case member, thereby eliminating the usual outer case member and the operations involved in forming and assembling the outer case member with the inner case member and the usual separate carrier.
The invention has the further advantage of eliminating the curling operation normally used to clamp the PTFE seal member between an inner and outer case member. The invention takes advantage of the one-piece carrier construction by employing a staking operating rather than the usual end curl, which is simpler to perform, requires fewer steps and less equipment, and yet achieves the end result of securely clamping the PTFE sealed on the carrier. Thus, the present invention greatly simplifies the construction and manufacture of seals.